What makes some men effeminate?

Not all effeminate men are gay and not all gay men are effeminate but there are those within the gay community who particularly fit stereotypes of gay men. When I consider the straight men who are effeminate it makes me really question what the hell is it exactly that causes this?? I've been trying to research it and cannot find much. I already know hormones have nothing to do with sexual orientation but do they play a part in effeminacy vs. masculinity? How much "girly" behaviour in a gay male is social or learned vs. biological predisposition? Is liking fashion and being sensitive something that you are born with and manifests in life as a result of your genetic design or do you just not fit within the group you were born into (masculine male) thus cling to the other (feminine female)? Of course much of what is distinctly male vs. female is still socially constructed but there must be SOME biological basis to it.